Various techniques of drilling underground arcuate paths are known in the art. Such techniques are useful in accomplishing many tasks, including placing pipelines and the like underneath surface obstacles such as rivers and highways. One such technique involves advancing a directional drill in an inverted arcuate path underneath, for example, an obstacle to establish an initial hole. The inverted path underneath the obstacle is completed when the drill assembly emerges from the earth within a preselected target area on the opposite side of the obstacle. A drill pipe, having been advanced in sections behind the drilling apparatus, remains in the hole and extends from the entry point on one side of the obstacle to the exit point on the other side of the obstacle. After the hole has been established, a hole-opening operation may be undertaken wherein the initial hole may be enlarged to a preselected diameter in order to accommodate, for example, a pipeline or electrical cable. In some cases the initial hole is properly sized for the contemplated end use, so this hole-opening operation is performed only if needed.
One technique of drilling a hole, opening the hole, and placing a pipeline or cable in the opened hole involves the use of a travelling rotary drive on an inclined ramp attached to the end of the pipe being placed in the hole. The travelling rotary drive includes means for rotating the pipe to facilitate drilling or manipulating the direction in which drilling will proceed. It is necessary in such systems to provide some means for moving the rotary drive up and down the inclined ramp. It is also necessary to provide some means for applying a pushing or pulling force to the end of the pipe being placed in or withdrawn from the hole.
Prior art systems have used a length of cable fixed at each end to an inclined ramp and a winch or drum mechanism on a travelling rotary drive to move the rotary drive up and down the ramp on a dolly and to apply the pushing or pulling force heretofore described. Such a system is disclosed in U.S. Pat. No. 3,878,903, entitled "APPARATUS AND PROCESS FOR DRILLING UNDERGROUND ARCUATE PATHS."